TurboTax does not support tax year 2020. You would need to seek out a local tax professional to assist you with the filing of a 2020 tax return.
To complete and file a prior year (2021 thru 2023) tax return using TurboTax you would need to purchase, download and install on a personal computer one of the desktop editions for each tax year required from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A prior year tax return can only be printed and mailed, it cannot be e-filed using TurboTax. Use a separate envelope for each tax year when mailing the tax returns.
